1. Technical Field
The embodiment of the disclosure relates to a matrix converter.
2. Related Art
A matrix converter includes a plurality of bidirectional switches that couple an AC power supply and a load together. Directly switching respective phase voltages of the AC power supply by controlling these bidirectional switches causes the output of an AC power with any voltage and frequency to the load.
In this matrix converter, the bidirectional switch switches the phase of the AC power supply to be coupled to the load. During this switching, a commutation operation that individually controls switching elements constituting the bidirectional switch in a predetermined order is performed. This suppresses a short circuit between phases for the input phase, circuit opening of the output phase, and similar trouble.
As a method of this commutation operation, a current commutation method and a voltage commutation method are known. In the current commutation method, for example, when there is a delay of polarity switching or a detection error of the electric current in the case where the output electric current is small, commutation failure such as circuit opening of the output phase might occur. In the voltage commutation method, for example, when there is a delay of switching of the magnitude relationship between the input phase voltages or a detection error of the voltage in the case where the difference in magnitude of the input phase voltages is small, commutation failure such as a short circuit between phases for the input phase might occur.
Thus, there has been proposed a technique that performs switching from the current commutation method to the voltage commutation method or switching reversed with respect to this switching in the case where the absolute value of the output electric current is small and in the case where the difference in absolute value of the input phase voltages is small, so as to perform the commutation operation (for example, see JP-A-2003-333851).